The present invention relates to an annular torsional rigid static component for an aircraft engine, the component comprises at least one means for mounting the engine to an aircraft.
The aircraft engine is preferably a jet engine. The term jet engine includes various types of engines, which admit air at relatively low velocity, heat it by combustion and shoot it out at a much higher velocity. Accommodated within the term jet engine are, for example, turbojet engines and turbo-fan engines. The invention will below be described for a turbo-fan engine, but may of course also be used for other engine types.
An aircraft engine of the turbofan type generally comprises a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. The core engine comprises a high pressure compressor, a combustor and a high pressure turbine in a serial relationship. The high pressure compressor and high pressure turbine of the core engine are interconnected by a high pressure shaft. The high-pressure compressor, turbine and shaft essentially form a high pressure rotor. The high-pressure compressor is rotatably driven to compress air entering the core engine to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor and ignited to form a high energy gas stream. The gas stream flows aft and passes through the high-pressure turbine, rotatably driving it and the high pressure shaft which, in turn, rotatably drives the high pressure compressor.
The gas stream leaving the high pressure turbine is expanded through a second or low pressure turbine. The low pressure turbine rotatably drives the fan and booster compressor via a low pressure shaft, all of which form the low pressure rotor. The low pressure shaft extends through the high pressure rotor. Most of the thrust produced is generated by the fan. Engine frames are used to support and carry the bearings, which in turn, rotatably support the rotors. Conventional turbo fan engines have a fan frame, a mid-frame and an aft turbine frame.
The structural strength of the aircraft engine hinges upon a limited number of such engine frames or structures, also known as cases or housings. These structures therefore represent the skeleton of the engine. The structures are highly loaded during operation of the engine. The structures usually comprise a bearing house for the engine shafts, a gas flow channel in the form of an annular duct and radial struts which form the link between the inner and outer parts of the engine. Thus the air is forced rearwardly through the openings between adjacent struts.
The engine is mounted to the aircraft wing via a mount system (normally a pylon and associated thrust links) at a forwardly located fan frame forward mount on the fan frame and at a rearwardly located turbine frame aft mount on the turbine frame. The function of these mounting means is to transfer load from the engine to the aircraft. Most often there are two types of mounting means in an engine, a first type that takes lateral and vertical loads and a second type that takes the load in the axial direction (thrust mounts).
It is desirable to achieve an annular static torsional rigid aircraft engine component with mounting means for connection to an aircraft, which creates conditions for a more lightweight engine.
In accordance with an aspect of the present invention, said mounting means comprises a body formed in a composite material. Composites are of lightweight and have a high specific stiffness and strength. Use of composites therefore make the engine's non-rotating, load carrying, structural component lighter while the stiffness and rigidity is substantially maintained.
According to a preferred embodiment, said composite body forms a wall structure. Such a wall structure encasing an internal chamber, one or several voids, or a through-hole creates conditions for a further lighter component in contrast to a solid unit. Further, said mounting means comprises a rigid member fitted tightly around the composite body and that the rigid member comprises a connection element for connection to the aircraft. By virtue of this design the mechanical load is distributed over a large surface in the composite to avoid local stress (compression) concentrations.
According to a further preferred embodiment, the component comprises a rigid annular support member and that the composite body is rigidly secured to said annular support member. By virtue of this design, a high torsional rigidity is achieved.
According to a further development of the last-mentioned embodiment, said rigid support member comprises an outer ring and an inner ring, that said mounting means is arranged between the inner and outer ring and that the composite body is rigidly connected to both rings thereby forming the torsional rigid unit.
Further advantageous embodiments and further advantages of the invention emerge from the detailed description below.